Norwich Roofers installs, repairs and maintains commercial roofs for businesses in Watton and across the wider Norfolk area.
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Commercial roofing covers everything from a small retail unit with a low-pitched felt roof to a large warehouse with a profiled metal sheet system. The work is different in scale and complexity from a domestic job, and the stakes are higher - a failed roof can make a building unusable and affect your business directly. We handle flat roofing, single-ply membranes, metal sheet roofing and built-up felt systems on warehouses, offices, schools and retail units.
Before any material is specified, the existing roof structure and deck need to be assessed. Insulation levels, deck condition, drainage layout and the height of upstands all affect which system will perform best. Getting this right at the specification stage saves money later and avoids the common mistake of laying a good system over a compromised substrate.
This page focuses on the materials and systems available for commercial buildings. There is no single right answer - each system has genuine advantages and real limitations, and the best choice depends on your building, your budget and how the roof will be used. What follows is an honest breakdown of each option.
Built-up felt roofing has been in use on commercial buildings in the UK for decades. It consists of multiple layers of bitumen-impregnated felt, torch-applied or cold-bonded in successive layers to build up a waterproof membrane. A mineral-surfaced cap sheet is added as the top layer.
The main advantages of a well-specified felt system are familiarity and cost. Most commercial roofers can install it, materials are readily available, and for a simple low-use flat roof it is a cost-effective solution. A three-layer torch-on felt system typically costs in the region of £40 to £70 per square metre installed, though access conditions and specification affect this.
The limitations are real. Felt is vulnerable to ponding water and UV degradation over time. Blistering - caused by moisture trapped beneath the layers during installation or by vapour from below - is a common long-term failure mode. On a large roof with significant plant traffic, felt is more susceptible to puncture than some of the alternatives. Felt roofs on commercial buildings typically last 15 to 25 years before a full replacement is needed, though this depends heavily on how well they are maintained and whether drainage is kept clear.
EPDM (ethylene propylene diene monomer) is a synthetic rubber membrane that has become increasingly popular on UK commercial buildings over the past two decades. It comes in large sheets that can cover a significant roof area with few or no joins, which removes one of the most common leak points in any flat roofing system.
EPDM is cold-applied using adhesive, which means no open-flame equipment and a simpler fire risk profile. This makes it particularly practical for occupied schools, offices and retail units where hot work creates complications. The material is highly flexible and accommodates thermal movement well - it does not crack or split under the stresses of repeated heating and cooling the way that older materials can.
EPDM membranes typically last 30 to 50 years in normal conditions. They are resistant to UV, ozone and standing water, which makes them well suited to roofs where drainage is imperfect. In terms of cost, EPDM typically falls in the £50 to £90 per square metre range installed on a commercial project, with price varying by thickness (1.0 mm, 1.2 mm and 1.5 mm are the common options - thicker is better for trafficked roofs), roof complexity and access.
Single-ply membranes are factory-manufactured sheets of thermoplastic material - most commonly TPO (thermoplastic polyolefin) or PVC (polyvinyl chloride). They are mechanically fixed or fully adhered to the roof deck, and seams are heat-welded rather than glued, which produces a strong continuous bond.
Single-ply systems are widely used on larger commercial and industrial roofs across the UK. The heat-welded seams, when done correctly by a competent installer, are as strong as the membrane itself and represent a significant improvement over the overlapped and bonded lap joints in older felt systems. TPO is also available in white and light grey, which can help with solar reflectance on buildings where summer heat gain is a concern.
Installation requires specific equipment for the hot-air welding of seams and a roofer who is familiar with the material. Single-ply systems are priced at roughly £60 to £100 per square metre installed on a commercial project. Lifespan is typically 25 to 40 years with appropriate maintenance.
Profiled metal sheet roofing - steel or aluminium panels fixed to a structural frame - is the standard for industrial buildings, large warehouses and agricultural units. It can also be used on extensions and covered walkways where the profile suits the building design.
Modern insulated metal roof panels (often called 'built-up' or 'composite' panels) sandwich a layer of rigid insulation between inner and outer profiled sheets. These offer better thermal performance than the older single-skin systems and are now the specification of choice for most new commercial and industrial builds.
Metal roofing is durable - steel systems with modern coatings are designed to last 30 to 40 years before significant work is needed. The main maintenance concern is the condition of the fixings and the seals around rooflights and penetrations. On older single-skin systems, the sealing washers on fixings can degrade and allow water ingress at thousands of individual points across the roof.
Insulation is often the area where money is saved at the specification stage and regretted over the life of the building. Under current UK Building Regulations, a new or replacement commercial roof requires insulation to meet minimum thermal standards. The required U-value for a flat roof on a commercial building is 0.18 W/m²K under Part L.
If your existing roof is being replaced, the insulation is almost always stripped and replaced as part of the work. Specifying the minimum required thickness is cheaper upfront but costs more in energy over time. Adding extra insulation beyond the regulatory minimum has a payback period through lower heating bills, and on a large building the sums are worth doing. Ask your roofer to price two or three insulation specifications alongside the membrane itself so you can make an informed choice.
On overcladding projects - where new metal sheets are fixed over an existing roof - existing insulation may be partially retained. The thermal performance of the retained insulation needs to be factored into the specification of any additional layer to ensure the overall U-value meets regulations.
Drainage design matters as much as the choice of membrane. A flat commercial roof needs to drain completely within 48 hours of rainfall. The falls in the roof structure or tapered insulation need to achieve a minimum of 1:80, though 1:40 is better practice. Outlets need to be sized for the roof area and local rainfall intensity, and there should be secondary overflow provision in case primary outlets block.
On a replacement project, it is worth reviewing whether the existing drainage is adequate or whether outlets need repositioning, upsizing or supplementing. Adding tapered insulation to create better falls is more expensive at the time but prevents the standing water problems that accelerate every type of roof covering.
Before you agree to any commercial roofing contract, some straightforward questions will tell you a lot about whether the roofer is the right fit for the job.
A roofer who answers these questions with specific detail is more likely to deliver a roof that performs as expected than one who talks in broad terms and pushes a single system regardless of the building.
Commercial flat roof replacement in the UK currently falls broadly in the following ranges, though every project is different and access, location and specification all affect the price.
Repairs and maintenance work is priced individually based on what the inspection finds. A single flashing replacement on an accessible roof costs far less than a large patch repair involving deck work. Getting a survey before committing to either repair or replacement is always the sensible first step.
We cover Watton and the wider Norfolk area from our base in Norwich. If you have a commercial building with a roof that needs attention - whether that is a repair, a like-for-like replacement or a change of system - call us to arrange a survey. We will give you a clear assessment of the roof's condition and a specific recommendation for what it needs, so you can make the right decision for your building and your budget.
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Call any time. Calls are answered day and night and passed straight to our roofers.
